renderAltered example

else {
        // Get tokens from the last field.         $last_field = end($this->view->field);
        if (isset($last_field->last_tokens)) {
          $tokens = $last_field->last_tokens;
        }
        else {
          $tokens = $last_field->getRenderTokens($fake_item);
        }
      }

      $value = strip_tags($this->renderAltered($fake_item, $tokens));
      if (!empty($this->options['alter']['trim_whitespace'])) {
        $value = trim($value);
      }
    }

    return $value;
  }

  /** * {@inheritdoc} */